23andMe Chromosome Segment Sharing

Since hearing about 23andMe finally bringing back the chromosome browsing feature that allows one to see one's matches with DNA Relatives on the site, we checked it out for our account (and that of our Haitian parent). For us, unfortunately, 23andMe still maxes out one's DNA matches at 5000. This means that the overwhelming majority of matches I have on that site are those sharing my "Hispanic" roots. For African matches, our Haitian parent has more luck. We were able to browse a number of them and see the shared segments with people from Nigeria, Congo (via South Africa), Sierra Leone, Ghana, Liberia, and other places. 

Interestingly, we saw that our Haitian parent shares a segment of DNA on their X chromosome that overlaps with that of a Fulani person (judging from surname) who is likely from Sierra Leone and someone else from Sierra Leone who is possibly Temne (inferring from surname). And through our Haitian parent's account, we saw that we share the Temne person as a match (even though 23andMe doesn't actually list this person in my DNA Relatives). In any case, the shared segments were always small (11.37 cM for the Temne, 11.58 cM for the Fulani). So, through our Haitian parent's side, we appear to have a female ancestor who was possibly from a Temne-like (or adjacent group) background who was trafficked to Saint Domingue. We assume the Fulani shares this Temne-like ancestry with us. But to make things more surprising, our parent did share a segment of DNA with another Fulani on the second chromosome that was assigned as "Senegambian and Guinean."

In terms of the paper trail, the colonial parish registries, runaway slave ads and notarized contracts or plantation inventories list a number of "nations" from what is now Sierra Leone and Liberia. Some examples include the Timbou, Mamou, Susu, and Mende. Cangas, Mesurades, Miserables, Bouriquis, and more from the Liberian and Ivory Coast regions were also present in the colony, according to Moreau de Saint-Mery. 

We will likely keep exploring this new shared segment viewing feature to explore our Haitian parent's matches with Liberians, Nigerians, and Ghanaians. It is just unfortunate that the Historical Matches feature doesn't allow for this. Nor can one see specific shared segments used by 23andMe to assign the African Genetic Group matches that appear in the Ancestry Composition breakdown. Adding these features would make the site more useful and important for genealogical research.